The present invention relates generally to an improved printing apparatus or composing system and tape-ribbon cartridge therefor, and more particularly, to a printing apparatus of the type having a printing station, a printing force exerting and resisting means, an image carrier and a font element with a raised character positionable in printing alignment with the printing station. The improvement of the present invention relates specifically to an improved means for exerting a printing force against the raised character on the font element and an improved means in the form of a tape-ribbon cartridge for supplying tape and ribbon to the printing station.
The printing apparatus of the present invention has particular application in the printing of relatively large characters for use in engineering drawing title blocks, flip charts, overhead transparencies, posters, silk screen stencils, signs, newspaper headlines and the like. These characters are generally much larger than most typewriters or other conventional means can generate. In the prior art four major methods have been used to create such letters: stencils, press-on letters, phototype setters and dry lettering printing processes. The application of stencils and press-on letters to form words, sentences is relatively time consuming. In addition, it is easy to misalign letters and get uneven spacing. Photo typesetting systems are rather large, expensive, permanent installations having several chemical baths that must be maintained. Further, a trained operator is necessary to get good results. Although the dry lettering processes presently used overcome many of the disadvantages and limitations of stencils, press-on letters and photo typesetters, a relatively large printing force is necessary to transfer an image of the desired character from the high-carbon content toners to the image carrier. Generally, the quality of the printing or the image transfer is dependent upon the magnitude of the printing force developed.
In prior art dry lettering systems, a variety of printing force exerting means have been utilized. One such means involves the use of a printing piston having a flat upper surface disposed in printing relationship with the printing surface. Such printing piston is lifted by a cam element, thereby creating a printing force to transfer an image to the image carrier. Another means for creating printing pressure is shown in U.S. Pat. No. 4,108,556 which utilizes a wedge-shaped element for creating the necessary printing force as it rolls across the printing station.